Project Abstract/Summary Type 1 Diabetes (T1D) is an autoimmune disease with both genetic and environmental contributions, yet a single environmental factor has yet to be identified. We propose that rather than the specific identity of the environmental factor, the way in which an environmental signal is received is most important to disease. Among individuals at risk of developing T1D, seroconversion to islet autoantibody (IA) production is the best and earliest biological predictor of disease progression. Thus, critical events leading to the destructive ? cell autoimmunity associated with T1D are linked to the development of IAs. In subjects with high risk HLA alleles, 9 gene regions marked by single nucleotide polymorphisms (SNPs) are associated with IA seroconversion. Our collaborator?s analysis of these IA risk loci reveals enrichment for genes/proteins that regulate only three cell signaling pathways (RAS/MAPK, PI3K/AKT and JAK/STAT), whereby four IA seroconversion risk variants (PTPN22, SH2B3, ERBB3 and UBASH3A) each impact all three. Thus, we propose that regulation of environmental sensing is at least in part controlled by the one or more of these risk variants associated with the development of IAs. Appropriate communication of the gastrointestinal tract (GI) with the environment is required for local and systemic immunologic homeostasis, which is in part regulated by the intestinal epithelial cell (IEC) through their physical and biochemical interactions with innate and adaptive immune populations. To this end, contribution of immunity within the GI tract to the expression of autoimmunity at distal sites has been previously demonstrated. Thus we propose that the seroconversion risk variants affect immune signaling pathways within the IEC contributing to the maintenance of autoimmunity in T1D, through the secondary expansion and/or polarization of autoreactive effector T-cells. To study human disease, a major need is cell-specific human isogenic systems that can be used to dissect the role of individual T1D risk gene variant alleles. Our preliminary studies support use of a disease-in- a-dish strategy that pairs human induced pluripotent stem cells (iPSCs) with CRISPR/Cas9 gene modification to fulfill these needs. We propose to couple iPSCs and CRISPR/Cas9 technology with our method of reproducible primary human IECs culture to achieve haploinsufficient, mono-allelic homozygosity at risk or protective alleles to evaluate alterations in IEC-immune mechanisms which contribute to the maintenance of ?cell autoimmunity.